Achievements
Complete each achievement to get the allotted gamerscore:

Turtle Tantrum! (5) - Destroy more than 5 enemies using a destructible object.
Invincible (5) - Complete a level without having to use a single Power-up.
Lean, Green and Mean (20) - Achieve more than 8,000 points.
Heroes in a Half Shell (30) - Complete the game with all 4 Turtles.
I Will Survive (30) - Complete a Survival Mode game. (Normal difficulty onwards)
Ice, Ice, Turtle (20) - Avoid Ice Ray traps in Level 8.
The Inflatable Reptilian Hero (5) - Get flattened by any trap.
Toe Be or Not Toe Be? (20) - Avoid all traps in Level 3.
Seen My Bones? (5) - Get zapped by any laser traps or attacks.
Turtle Power (25) - Complete the game in Story Mode. (Normal difficulty onwards).
Slow as a Turtle (10) - Complete a level in under 3 minutes.
Staying Alive (25) - Defeat the Final Boss without dying.

Unlock Levels for Quickplay Mode
Play story mode and defeat the boss at the end of a level to unlock that stage in quickplay mode.

Keep The Score After Losing All Lives
After getting the game over screen, DO NOT CONTINUE. Instead let the game take you back to the main menu and then choose "Continue Game". You'll start at the beginning of the level that you died on, along with the points that you had when you entered the stage. NOTE: This doesn't work on stage 1.